Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MiceAndMen]

Tepco provided more details to NISA about the water purification unit which is supposed to start running at Fukushima Daiichi in the coming days. The following attachment includes a number of diagrams, photographs and a map showing the locations of the facilities and the new tanks : http://www.meti.go.jp/press/2011/06/20110609002/20110609002-3.pdf

Do we know when this is supposed to come online? Initially I recall seeing 15 June as the date. I remember thinking yesterday, "1 week to go". But later yesterday I saw a couple of things that said 25 June. I need to find some references, but if the 25 June date is correct then there has been a 10 day slip in the schedule.

 

[MiceAndMen]

The debris was scattered on top of the fuel assembly tops. They all looked in place to me. The rectangular patterns are quite distinctive. The only thing is that we only saw about two - three square feet of the top of the assemblies. The key in the video is to look quickly at the very beginning. As the bubbles come up and block the lens you can see the pattern of the top of the assemblies at the top and left of center. That rectangular pattern was consistent with the pattern in the reactor 4 SFP.

http://www.dailykos.com/story/2011/05/11/974605/-Up-Date-with-SFP-3-Video

The blog you linked to says

Hard to tell if there's any damage to the fuel assemblies when you can't see them for all the rebarb, concrete, cables and other crap.

and I agree with that. I just re-watched that video again and I can't see anything anywhere close to what you're describing. I looked at the very beginning, where the bubbles come up and impede the view. I don't see any rectangular patterns at all. Perhaps you could post a still frame from the video and circle the rectangular pattern you see.

 

[Atomfritz]

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/25/028/25028788.pdf

it's too highbrow for me to understand

but some of you folks will devour it.

old jim

old jim, thanks for the link, i devoured it... :)

...and learned new things even though i understood only about 1%.
didn't know before that hydrogen burning/deflagration/detonation can be in an oscillating manner.

does anybody know the resonance frequencies of the blown-up building parts?

i ask because if by chance the buildings got into resonation this could mean that the effects got way more violent than normally to be expected from some explosive.
with resonance you can get very destructive effects with minimal energy input.

if this happened then maybe the hydrogen quantities necessary to get such effect could be way smaller than commonly estimated!

maybe an amount of hydrogen that nominally would only deflagrate causing only minor damage could do violent and destructive effects like this if it just was oscillating on the "right" frequence?

Since the concern is that it is salt water, no doubt from tsunamis, and that it is contaminated raises a host of questions.

Indeed. We are in for some more surprises, I bet.

... worst case versus best case (normally officially supported by TEPCO), you can predict with 80% likelihood that it will be more than 40%, ...

But they count only air release ? Or water also ?

Care to share your rough calculations?

Look, they reported 720k TBq in just 10k cubic meters of water.
They reported more than 800k TBq as airborne release in the first weeks of the accident alone.

This "official" radiation release is way more than 40 Megacuries. And this may be just a few percent of the actual/future releases.

You never know if that accounts for all possible fission products and their decay chain or just for one isotope. But this really matters.

Anyway, the way most important point is that this contamination for most part did NOT get fixed/trapped/caught in land soil as at Chernobyl, but will be ionically distributed over the whole world.
Really, immobile cesium stuck in soil of a "death zone" is not really a threat. Dissolved cesium in ionic form contaminating the oceans... ...this is a worldwide threat.

But I fear that this point will get noticed only a few years later, when it gets difficult to find fish below acceptable radiation levels.
Then this could become a global problem.

 

[tsutsuji]

Do we know when this is supposed to come online? Initially I recall seeing 15 June as the date. I remember thinking yesterday, "1 week to go". But later yesterday I saw a couple of things that said 25 June. I need to find some references, but if the 25 June date is correct then there has been a 10 day slip in the schedule.

I have not heard about this 25 June delay. Most Japanese news media are still relying on the 15 June starting schedule. It was also announced that on June 10th the facility will be tested using low level contaminated water : http://news.tbs.co.jp/newseye/tbs_newseye4747210.html

 

[Atomfritz]

Do we know when this is supposed to come online? Initially I recall seeing 15 June as the date. I remember thinking yesterday, "1 week to go". But later yesterday I saw a couple of things that said 25 June. I need to find some references, but if the 25 June date is correct then there has been a 10 day slip in the schedule.

First the schedule was June 1st, as many Tepco press releases insisted.
So it should already be online.
This postponement onto Jun 25 looks like a waiting for Godot.

 

[etudiant]

I have not heard about this 25 June delay. Most Japanese news media are still relying on the 15 June starting schedule. It was also announced that on June 10th the facility will be tested using low level contaminated water : http://news.tbs.co.jp/newseye/tbs_newseye4747210.html

June 25 would make sense in light of TEPCOs well publicized efforts to find additional storage space combined with their comments that the site would overflow by June 20th.
It had been a bit inconsistent to envision processing 1200 tons/day starting June 15 and yet still having the site overflow on June 20. One explanation was anticipated heavy rains, but this idea of a start up delay is much more likely.

 

[clancy688]

Look, they reported 720k TBq in just 10k cubic meters of water.
They reported more than 800k TBq as airborne release in the first weeks of the accident alone.

If I'd get a cookie every time I have to explain the differences between those activity numbers, I could probably build a castle out of them by now.

You CAN'T compare the 720 TBq activity for the basement water and the 760k TBq airborne release.

The 760k TBq airborne release is an estimate which only covers I131 and C137 isotopes. Furthermore, it's a converted value. Basically it's (I131 release in Tbq * 1 + C137 release in TBq * 40). The real, measurable activity of those 770k TBq is in fact 160k TBq I131 and 15k TBq C137.
Everything regarding converting values is described in the INES Manual. Page 5 and page 15f.

The 720k TBq water number is NOT converted. It's a normal addition of the activity of the three isotopes I131, C134 and C137 in the basement water. So it's way more than the airborne release. If all those isotopes in the basement get released into the environment, Chernobyl won't be the biggest radioactive release in human history any more...

 

[Atomfritz]

If I'd get a cookie every time I have to explain the differences between those activity numbers, I could probably build a castle out of them by now.

You CAN'T compare the 720 TBq activity for the basement water and the 760k TBq airborne release.

The 760k TBq airborne release is an estimate which only covers I131 and C137 isotopes. Furthermore, it's a converted value. Basically it's (I131 release in Tbq * 1 + C137 release in TBq * 40). The real, measurable activity of those 770k TBq is in fact 160k TBq I131 and 15k TBq C137.
Everything regarding converting values is described in the INES Manual. Page 5 and page 15f.

The 720k TBq water number is NOT converted. It's a normal addition of the activity of the three isotopes I131, C134 and C137 in the basement water. So it's way more than the airborne release.

Thank you for pointing out what I meant with "You never know if that accounts for all possible fission products and their decay chain or just for one isotope. But this really matters."

If all those isotopes in the basement get released into the environment, Chernobyl won't be the biggest radioactive release in human history any more...

Ermm, are you really that optimistic that these isotopes will be contained? I am not :(

 

[tsutsuji]

An English version is now available for Tepco's Summary of radioactive accumulated water treatment system : http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110609e8.pdf

 

[StrangeBeauty]

The debris was scattered on top of the fuel assembly tops. They all looked in place to me. The rectangular patterns are quite distinctive. The only thing is that we only saw about two - three square feet of the top of the assemblies. The key in the video is to look quickly at the very beginning. As the bubbles come up and block the lens you can see the pattern of the top of the assemblies at the top and left of center. That rectangular pattern was consistent with the pattern in the reactor 4 SFP.

http://www.dailykos.com/story/2011/05/11/974605/-Up-Date-with-SFP-3-Video

The blog you linked to says "Hard to tell if there's any damage to the fuel assemblies when you can't see them for all the rebarb, concrete, cables and other crap." and I agree with that. I just re-watched that video again and I can't see anything anywhere close to what you're describing. I looked at the very beginning, where the bubbles come up and impede the view. I don't see any rectangular patterns at all. Perhaps you could post a still frame from the video and circle the rectangular pattern you see.

I believe the original reference was to this:


I think Joe means starting at 0:27 if you look in the upper left corner you see the top of a few of the fuel assemblies. I'm with the dkos user and MiceAndMen here; I can't tell much of anything about the state of the fuel from that brief imagery.

I also didn't feel I could tell much about the actual state of the assemblies in the SPF4 video either. The tops of the assemblies seemed to be somewhat intact. Can't draw conclusions about lower down where the fuel itself is, but at least it wasn't all in shambles.

 

[Quim]

If all those isotopes in the basement get released into the environment, Chernobyl won't be the biggest radioactive release in human history any more...

But wouldn't it be cheaper for Tepco to just dump that water into the Pacific?
I honestly believe that the UN, or a representative of the Pacific rim nations should be at that site monitoring discharge into the ocean.

 

[clancy688]

Thank you for pointing out what I meant with "You never know if that accounts for all possible fission products and their decay chain or just for one isotope. But this really matters."

Sorry, I missed that statement. ;)Here's a detailed list of all basement water and its activity: http://www.tepco.co.jp/cc/press/betu11_j/images/110603a.pdf

I used it to calculate only the C137 in the water. Out of the 720k TBq total activity, 141k TBq accounts for C137.

That's half of the total C137 inventory of the Chernobyl core. Half of a Chernobyl core's worth of C137 dissolved in the basements. Total airborne release of C137 at Chernobyl was btw 85k TBq.

I didn't calculate the C134, but the numbers are nearly identical to C137, so it's probably around 140k TBq. Again, that's more than half of a Chernobyl core's worth of C134.

Just to visualize that: There's practically one half of a Chernobyl sized core spread out in the catacombs of a six reactor nuclear plant. Have fun cleaning up that mess.Edit: Big calculation mistake - the number is actually less than half of the original number. Guess that's a hint for me to go to bed. Which I'll do.

Edit 2: But one last interesting observation - the I2C ratios in Units 1-4.

The initial ratio should be 8:1.

The measurement in Unit 1 was taken on March 26th, two weeks after the accident. That's two halftimes, so the ratio should be 2:1. And it's 1:1

The measurement in Unit 2 was taken on March 27th, two weeks after the accident. That's two halftimes, so the ratio should be 2:1. And it's 3:1.

The measurement in Unit 3 was taken on April 22th, five weeks after the accident. That's five halftimes, so the ratio should be 1:4. It is 1:2. Does this look like recriticality? At least I don't think so...

 

[rowmag]

The NISA has summarized a number of informations about the water treatment facility in http://www.meti.go.jp/press/2011/06/20110609006/20110609006-2.pdf (in Japanese).
[...]
2,000 m³ of radioactive sludge will be produced. 400 caesium absorption towers will be spent. The caesium absorption towers are installed in concrete box culverts. The sludge in pellet containers at the process main building. The absorption towers are designed to ensure that in a worse case scenario they don't heat more than 1°C per hour. The sludge will have a cooling system to remove the residual heat. Hydrogen production will be controlled with ventilation.

So even the sludge needs to be cooled and hydrogen production dealt with.
It just never gets easy, does it?

There is no fear of criticality, because no U or Pu is present in the water.

Why is there no U or Pu in the water? Wasn't this water flushed through the melted and crumbled cores?

 

[MiceAndMen]

I have not heard about this 25 June delay. Most Japanese news media are still relying on the 15 June starting schedule. It was also announced that on June 10th the facility will be tested using low level contaminated water : http://news.tbs.co.jp/newseye/tbs_newseye4747210.html

I was just about to give up searching, and found this:
http://www3.nhk.or.jp/daily/english/09_05.html

The company says it is determined to begin operating the water-decontaminating system by June 25th at the latest.

That's where I saw it yesterday and it appears the wording has slightly changed. That doesn't exactly inspire confidence that it will be up and running on the 15th.

 

[robinson]

WIDEN, Evac Zone: Greenpeace — Minute amounts of radioactive strontium have been detected in soil at 11 locations in Fukushima Prefecture, including the city of Fukushima 62 km from the crippled nuclear power plant, according to the science ministry.

...

According to the Education, Culture, Sports, Science and Technology Ministry, 54 becquerels of strontium-89 per kg were detected in soil collected in the city of Fukushima on April 27.

The highest amount, 1,500 becquerels of strontium per kg, was detected in soil collected May 6 in the town of Namie, 24 km northwest of the nuclear plant.

The ministry also detected 1,000 becquerels of strontium per kg in the village of Iitate, 220 becquerels in the town of Kawamata and 30 becquerels in the town of Hirono.

http://search.japantimes.co.jp/cgi-bin/nn20110610a2.html

 

[Jorge Stolfi]

Forget the steam explosion for a moment, let's try and figure what vectored energy upwards [in unit #3].

Sorry, but I cannot see the explosion as being "vectored upwards".

If that did happen, we would see a jet of gas moving VERY fast at the beginning, then slowing down VERY quickly to a halt, after traveling a fairly short distance. That is because once the hot gas leaves the "muzzle" it will be propelled forward only by its inertia, which has to overcome the intertia of the (denser) air above the building. That is, in fact, what we see during the intial phase of the explosion --- but directed horizontally, on both sides of the building.

Instead of the vertical "vectoring", what I see instead, after the horizontal explosion(s), is a fairly slow and steady rise of the gas column, as could be expected to result from buoyancy alone. The narrowness of the column is a normal effect in such situations: the colder air on the sides is under higher pressure than the warm gas in the column, so it moves inwards, squeezing the column. Meanwhile the gas at the top of the column gets stopped by the cold air above, and is then pushed aside by the rising gas in the column, creating the mushroom's cap. Eventually all the gas originally in the column ends up in the cap.

Thus, one does not need any vertical "vectoring" of the blast to explain the narrow rising column. A vectored blast could have occurred, and could have contributed some momentum to the rising column as it got started --- but I see no evidence that it actually did.

Moreover, the state of the building after the explosion actually provides several bits of evidence against the vectored blast theory. The massive frame of the overhead crane seems to have fallen on the service floor straight down; and the winchbox is still sitting on top of the crane, as if it had fallen straight down too. Also, the only roof beam that is still attached to the building's wall is precisely the one which passed over the reactor pit.

Furthermore, we have seen close-up video frames of the gate that leads from the reactor pit to the steam-dryer storage pool. That gate is a stack of several concrete pieces that slide into grooves or ridges on either side of the pool. If the hypothetical reactor blast was so forceful as to snap the RPV end-cap bolts and eject part of the fuel, one would expect it to also dislodge or damage those blocks; but they look quite intact.

Finally, if the reactor had exploded upwards, several items would have been blown out of the way: the steam dryer-separator (a bunch of organ-pipes and baffles ~5 meters wide and ~3 meters tall), the pressure vessel cap, the bright yellow drywell cap (~9 meters wide), and the reactor shield plugs (six semicrcular concrete "waffles", each ~10 m wide). I looked hard at all the highest-resolution pictures available, but could not find any hint of any of those items anywhere, on or around #3.

On the other hand, I am willing to consider the hypothesis that there was (and there still is) a major leak from the RPV into the refueling pit, and from there to the service floor. I am not sure about the route; but we now know that the RPV was breached by the meltdown of the core, so the steam would have been dumped into the drywell. From there, the steam could have leaked through a breach anywhere on the drywell's wall into the 5 cm gap between the drywell and the surrounding concrete, and then sneaked up that gap to the refueling pit. Or it could have breached the diaphragm and bellows seal at the top of the drywell, and then burst into the pit by breaching the drywell cap or its gasket. Either way, I believe that steam from the RPV/drywell has been leaking out of the refueling pit since the explosion, and is the main source of the #3 steam plume(s).

This leak may have been the source of the hydrogen, or may have set off the explosion; but, given all the evidence above, I don't see how it could have, by itself, caused much damage to the building.

 

[Bioengineer01]

Care to share your rough calculations?

At the moment I have an issue with people stating that releases must be 50% or more of Chernobyl by now. They might be, I don't have problem imagining such a possibility, but I don't remember seeing evidence that makes this a relatively safe bet.

How much do we think got into the sea? I understand the estimate for the radiation in the water that is still in basements & trenches or moved to storage is about the same as the estimated air release. But I don't remember any good estimates for what's already gone into the sea.

I can't help but be a bit grumpy about this stuff at the moment because although its very important and I expect the reality is quite bad, I am not happy that the doubling of an estimate is being treated as news that radioactive release is worse than we thought weeks ago. Its mostly the media I am unhappy with about this, although it may have happened a little on this forum too. I mean seriously, the estimate that was recently increased was the one that was ignored when it first came out because it was the lower of two estimates that came out at about the same time, and the other higher one was not so far off the new 'double' estimate we now have. So its really not double the number most of us would of had in our minds weeks ago.

http://www.dbune.com/news/business/5345-seawater-near-fukushima-plant-75-million-times-over-legal-radiation-limit.html
"

However, it is still not the highest level because radioactive iodine in the water inside reactor 2's cracked storage put yielded on Saturday 5.2 million becquerels per cubic centimeters or 130 million times the legal limit, while water leaking from the crack read 5.4 million becquerels.

"
http://www.mofa.go.jp/j_info/visit/incidents/llc_water.html
"(

2) This contrasted sharply with the 5.2 to 5.4 million Bq/cc contained in the water in a pit near Unit 2 or the water being leaked into the ocean.

"
http://www.nytimes.com/2011/04/04/world/asia/04japan.html?_r=1&ref=world
"

Experts estimate that about seven tons an hour of radioactive water is escaping the pit.

"
5.4x10^6 Bq/cm^3 => 5.4x10^12 Bq/m^3
7 Tons/hour => 168 Tons/day
I am conservatively assuming that this went on for 21 days, then 168 Tons/day * 21 days =
3528 Tons that alone means that ~19,000 x10^12 Bq went to the Ocean for this cause alone.
If you now assume a continuous leak of the same type of water from the cracks in the basements foundations, as shown by our new geologist through the rain water drains to the Ocean at a very conservative number, let's say 1/4th the volume as before, but for 4 times as many days, so another 19,000 x 10^12 Bq, that is 38,000 Terabequerels additional to the estimate of 850,000 (http://www.google.com/url?sa=t&sour...sg=AFQjCNGfmzzCqGOPxsbTGOQZeNUAWyFniQ&cad=rja), bringing us up to around 900,000 Terabequerels. Your comparisson to Chernobyl at this stage depends on what do you compare it with, if you use "official" Chernobyl values as reported 90 days after that crisis started, we are already above them.

 

[etudiant]

Part 3 of the Asahi Shimbun series on the Japanese nuclear experience is here:
http://www.asahi.com/english/TKY201106090181.html

Note that it is more oriented to the social impact and perhaps would be better placed in another thread

 

[robinson]

A brief pause from the technical/physics things to say to all who have contributed here, thanks. I've been reading since the start, try to follow up on the links (and fail miserably), tried to contribute when I can, and have enjoyed this topic as much as anything on the internet.

Since it seems the topic will continue for a very long time to come, I just wanted to say thanks to all, as well as the people being linked to for information.

 

[tsutsuji]

I was just about to give up searching, and found this:
http://www3.nhk.or.jp/daily/english/09_05.html

That's where I saw it yesterday and it appears the wording has slightly changed. That doesn't exactly inspire confidence that it will be up and running on the 15th.

What appears to be the original Japanese news at http://www3.nhk.or.jp/news/html/20110609/t10013409631000.html says the following :

A) The decontaminating system will start running approximately on June 15th (literally on June 15th or a few days sooner or later).

B) By raising the level in the process main building up to 1.4 m above the floor of the 1st basement, Tepco is winning an additional 2700 ton storage capacity, which is the amount covering the needs for 5 days. So instead of being June 20th, the day when the water might overflow is delayed to June 25th. But Tepco is confident that the decontaminating system will have started running by that date.

So my understanding is that the schedule is left unchanged, but the safety margin is increased from 5 to 10 days.

　

 

[desertlabs]

I just now recalled that I posted this here, a month or so ago (#5257):

<<When TEPCO tells me it's 10% of Chernobyl, I'll assume it's most likely at least 20%, and I'm fairly sure that I at least won't be way high.
Could I be way low? Yeah, I suppose so, but I'll wait for better evidence to support that.
(And, if it *is* way low, there will surely be evidence of that, eventually. Even if it takes a while to seep out, so to speak.)>>

So what did they announce yesterday? That it's more like 20%.

(I'm now working off the assumption it's probably really more like 40%, but we'll see what happens.)

I'm sorry, but this is sending me 'round the bend. Am I wrong or was the "initial" estimate of 370,000 becquerals for the MONTH following the "accident", and the new estimate of "double" is for the first WEEK after the "accident". So what is it now 6/9...I feel like I'm in the Twilight Zone.

 

[Quim]

...If that did happen, we would see a jet of gas moving VERY fast at the beginning, then slowing down VERY quickly to a halt, after traveling a fairly short distance. That is because once the hot gas leaves the "muzzle" it will be propelled forward only by its inertia, which has to overcome the intertia of the (denser) air above the building.

That is, in fact, what we see during the intial phase of the explosion --- but directed horizontally, on both sides of the building.

Instead of the vertical "vectoring", what I see instead, after the horizontal explosion(s), is a fairly slow and steady rise of the gas column, as could be expected to result from buoyancy alone.

The narrowness of the column is a normal effect in such situations: the colder air on the sides is under higher pressure than the warm gas in the column, so it moves inwards, squeezing the column.

Meanwhile the gas at the top of the column gets stopped by the cold air above, and is then pushed aside by the rising gas in the column, creating the mushroom's cap.

Eventually all the gas originally in the column ends up in the cap.

Thus, one does not need any vertical "vectoring" of the blast to explain the narrow rising column.

A vectored blast could have occurred, and could have contributed some momentum to the rising column as it got started --- but I see no evidence that it actually did.

Moreover, the state of the building after the explosion actually provides several bits of evidence against the vectored blast theory.

The massive frame of the overhead crane seems to have fallen on the service floor straight down; and the winchbox is still sitting on top of the crane, as if it had fallen straight down too.

Also, the only roof beam that is still attached to the building's wall is precisely the one which passed over the reactor pit.

Furthermore, we have seen close-up video frames of the gate that leads from the reactor pit to the steam-dryer storage pool.

That gate is a stack of several concrete pieces that slide into grooves or ridges on either side of the pool. If the hypothetical reactor blast was so forceful as to snap the RPV end-cap bolts and eject part of the fuel, one would expect it to also dislodge or damage those blocks; but they look quite intact.

Finally, if the reactor had exploded upwards, several items would have been blown out of the way: the steam dryer-separator (a bunch of organ-pipes and baffles ~5 meters wide and ~3 meters tall), the pressure vessel cap, the bright yellow drywell cap (~9 meters wide), and the reactor shield plugs (six semicrcular concrete "waffles", each ~10 m wide). I looked hard at all the highest-resolution pictures available, but could not find any hint of any of those items anywhere, on or around #3.

On the other hand, I am willing to consider the hypothesis that there was (and there still is) a major leak from the RPV into the refueling pit, and from there to the service floor. I am not sure about the route; but we now know that the RPV was breached by the meltdown of the core, so the steam would have been dumped into the drywell. From there, the steam could have leaked through a breach anywhere on the drywell's wall into the 5 cm gap between the drywell and the surrounding concrete, and then sneaked up that gap to the refueling pit. Or it could have breached the diaphragm and bellows seal at the top of the drywell, and then burst into the pit by breaching the drywell cap or its gasket. Either way, I believe that steam from the RPV/drywell has been leaking out of the refueling pit since the explosion, and is the main source of the #3 steam plume(s).

This leak may have been the source of the hydrogen, or may have set off the explosion; but, given all the evidence above, I don't see how it could have, by itself, caused much damage to the building.

I intended to edit down your response (for I am a draconian editor of other people's text) but I found nothing extraneous at all I admire that kind of writing.

Thank you Jorge, I like your insights please allow me to offer you this view, our views contrast well with each other. I don't see any conflicts at all.

I do see another paradigm in the same picture you paint though.

I also see an extremely hot, steamy, hydrogen rich atmosphere in the Dry Well.

There were broken pipe(s) venting hot steam and gases directly off the "pile" into the drywell. The water being poured into the RPV was coming in the well as steam - that was the intent. Along with the steam came a steady stream of hydrogen.

The Drywell became an immensely hot cauldron of hydrogen and steam under a steadily increasing pressure and temperature.

Just before the number three blast, the atmosphere in the well was at least 60 psi, because we know that elsewhere a Mark I had started leaking somewhere around that pressure. The Japanese are good craftsmen and they made their own octagonal pattern for the lid so it may that those lids held up to 125 psi. It doesn't much matter what the actual pressure was the first time the lid was lifted enough to send a jet of this chamber gas to the realms above.

The sequence came as a result of trace amounts of oxygen which began developing inside the leaky containment - we know there were sources for at least a small amount of oxygen production in there.

So, in the reciprocal of what we in our normal world see, a gaseous mixture "flashed over": this may have been triggered by a sharp reduction in pressure as when the steam pressure forced the lids to float a little bit.

At the time just before the blast, the lid(s) had been seeping hydrogen into the region of the cattle trough, where it was beginning to rise up in a column of an explosive hydrogen/oxygen mixture.

This had to have occurred on the south side of the Lid matrix structure - a jet of gas found a path out and forced the crack a little wider. Then the pressure reduction set off a flash-over (unless it was visa versa and a flash over forced a path, lifting (tilting) the lid structure up on the south side.

Which set off all the gases in the region above the lid.
Thus an explosive wave traveled down the cattle chute southbound.

I don't see any likelyhood that the head bolts stretched nor would they be needed to stretch under either of our specific views. If they did, fine, if they didn't they weren't needed anyway, the pathway to the drywell was already open.

I don't see any reason to think the steam-dryer storage pool was involved in any significant way other than as a passageway for water or steam.

Are we together so far?

If so, we shall continue.

 

[MiceAndMen]

What appears to be the original Japanese news at http://www3.nhk.or.jp/news/html/20110609/t10013409631000.html says the following :

A) The decontaminating system will start running approximately on June 15th (literally on June 15th or a few days sooner or later).

B) By raising the level in the process main building up to 1.4 m above the floor of the 1st basement, Tepco is winning an additional 2700 ton storage capacity, which is the amount covering the needs for 5 days. So instead of being June 20th, the day when the water might overflow is delayed to June 25th. But Tepco is confident that the decontaminating system will have started running by that date.

So my understanding is that the schedule is left unchanged, but the safety margin is increased from 5 to 10 days.

OK, that makes sense. Thanks. I hope they do get it running next week.

@robinson, don't forget the moderators and mentors. They do a great job keeping things on-topic without being too heavy-handed. They deserve many thanks.

 

[benzyme]

I don't recall seeing this issue discussed? A known problem with unexpected pressure events and steam dryers in BWRs...it's a little too technical for me, but others might find interesting:

http://mydocs.epri.com/docs/Nuclear/Steam Dryer Methodologies Dec08.pdf

 

[clancy688]

I am conservatively assuming that this went on for 21 days, then 168 Tons/day * 21 days =
3528 Tons that alone means that ~19,000 x10^12 Bq went to the Ocean for this cause alone.

TEPCO made an own estimate of the amount which flowed through that crack into the sea.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110421e2.pdf

that is 38,000 Terabequerels additional to the estimate of 850,000 (http://www.google.com/url?sa=t&sour...sg=AFQjCNGfmzzCqGOPxsbTGOQZeNUAWyFniQ&cad=rja), bringing us up to around 900,000 Terabequerels. Your comparisson to Chernobyl at this stage depends on what do you compare it with, if you use "official" Chernobyl values as reported 90 days after that crisis started, we are already above them.

Sigh...

One page earlierer I explained why you can't compare those official airborne release values to any other activity values. Why do people keep ignoring my posts? https://www.physicsforums.com/showpost.php?p=3348281&postcount=9472

Btw, do you have those "official Chernobyl values as reported 90 days after that crisis started"? I'd be interested in them...

 

[Calvadosser]

I don't recall seeing this issue discussed? A known problem with unexpected pressure events and steam dryers in BWRs...it's a little too technical for me, but others might find interesting:

http://mydocs.epri.com/docs/Nuclear/Steam Dryer Methodologies Dec08.pdf

Interesting document, thank you.

I remember a long time ago (early 1970's) a colleague who was an acoustics expert went for a job interview with a nuclear power organisation. Later, someone asked him what acoustics had to do with nuclear power. He replied that sound levels inside reactors can be high enough to break things, so there were plenty of problems needing acoustics expertise in the nuclear industry.

 

[benzyme]

Here's another document from the NRC on the issue:

http://www.nrc.gov/reading-rm/doc-collections/commission/secys/2004/secy2004-0104/attachment4.pdf

 

[razzz]

I don't recall seeing this issue discussed? A known problem with unexpected pressure events and steam dryers in BWRs...it's a little too technical for me, but others might find interesting:

http://mydocs.epri.com/docs/Nuclear/Steam Dryer Methodologies Dec08.pdf

Basically says during certain conditions steam will created back pressure with irregular flows when valve(s) cause vibrations by emitting a certain kind of sound waves...in other words: internal whistling.

 

[tsutsuji]

Tepco's request to NISA to keep unit 2's double doors open : http://www.nisa.meti.go.jp/english/press/2011/06/en20110609-5.pdf (in English)

 

[~kujala~]

TEPCO made an own estimate of the amount which flowed through that crack into the sea.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110421e2.pdf

Yes, their estimate for unit #2 leak was 4 700 TBq for April 1st - April 6th.

The problem with this calculation is that seawater was already contaminated before April 1st as can be seen from these charts:
http://varasto.kerrostalo.huone.net/leak_1.png
http://varasto.kerrostalo.huone.net/leak_2.png

On the other one can see from the above charts that seawater contamination has been going steadily down after they were able to plug the leak. So there is no proof that groundwater is heavily contaminated and that heavily contaminated groundwater would flow towards sea. If this would be happening the seawater radiation levels would not decrease.

The explosion of the unit #2 happened March 15th and if we assume one day break before the leak started one could assume the starting day of the leak to be March 16th.

A simple calculation then tells that instead of 6 days we could assume 16 + 6 days and if we assume a constant level of contamination the total amount of the leak would be 17 200 TBq.

Some smaller scale leaks also after April 6th can be assumed and on the other hand it is possible that just after March 15th the contamination level was higher than what has been calculated between April 1st - April 6th.

So to put it on the safe side a wild guess of 50 000 TBq could be made including all leaks (iodine + cesium134/137) between March 11th - May 11th.

Edit: This estimate only concerns water outside silt fences ie water that has really flown into the sea. The water inside silt fences belongs to a category "to be processed". They installed silt fences April 11th - april 13th:

In order to prevent water containing radioactive materials from spilling
from a plant's port to the sea, we installed 120 meter wide silt fences
(double layered) around a breakwater on the south of the station at 10:45
am on April 11. ...
At 1:50 pm on April 13, we installed silt fences
(double layered) in front of the screen of Unit 3 and 4. At 0:20 pm on
April 14, we installed silt fences in front of the screen of Unit 1 and 2,
and in front of intake of water.

http://www.houseofjapan.com/local/fukushima-reactors-status-15-apr

 

[elektrownik]

Tepco's request to NISA to keep unit 2's double doors open : http://www.nisa.meti.go.jp/english/press/2011/06/en20110609-5.pdf (in English)

in order to implement calibration of water level gauges of the Reactor Pressure Vessel and the Primary Containment Vessel

Is there water level sensor in drywell ?

 

[zapperzero]

Hold a second and sorry if it is just another stupid comment on my part, but if it wasn't the containment that vectored the detonation (second phase), for that amount of vertical energy to be generated you'd need fusion level releases of energy from the SPF, since the pool is such a poor vertical vectoring structure. Is it conceivable that the pressure wave from the first detonation could have triggered a fusion reaction? Or am I having a serious senior moment here?

Why is it poor? Anyway, no fusion... if it were that easy, we'd have done it by now and there would not be any nuclear plants in existence :D.

 

[zapperzero]

On the other hand, is it much more surprising than the presence of contaminated water at Fukushima Daiichi unit 6 ? Or at any garden pond or swimming pool in the nearby cities and villages ?

Yes, it is. The fact that it is inside a building MUST have protected it from fallout. So, it MUST have been contaminated when it came in.

EDIT: For once, I tend to believe TEPCO.

 

[etudiant]

Yes, it is. The fact that it is inside a building MUST have protected it from fallout. So, it MUST have been contaminated when it came in.

EDIT: For once, I tend to believe TEPCO.

The TEPCO scenario as outlined seems very implausible, imho.
The initial tsunami which flooded the plant was clean, unless the ocean off the plant was already seriously contaminated.
There has been no subsequent flooding and the only additional seawater intake is for the cooling.
Again, if that cooling water is contaminated and leaking in the plant, it might be an explanation, but it would require the water off the site to be very active.
The easiest explanation would seem to be that something is amiss at DaiNi, fortunately much less so that at DaiIchi.

 

[tsutsuji]

Is there water level sensor in drywell ?

I checked the Japanese version (attachment No. 1 of http://www.meti.go.jp/press/2011/06/20110608002/20110608002.html ), and I think there is no translation mistake. I have no clue about the real meaning of that sentence.

Yes, it is. The fact that it is inside a building MUST have protected it from fallout. So, it MUST have been contaminated when it came in.

EDIT: For once, I tend to believe TEPCO.

Contaminated ground water may have seeped in through new earthquake-created cracks in concrete, or through cracks older than the earthquake. We had a discussion about these possibilities for Fukushima Daiichi unit 6 at https://www.physicsforums.com/showthread.php?p=3336401#post3336401 .

The TEPCO scenario as outlined

Outlined by whom ? Did Tepco publish a press release on this topic ? Did Tepco provide any scenario ?

The third sentence from the bottom of http://jp.ibtimes.com/articles/19498/20110608/1307540621.htm translates as "This time, the contaminated water intended for sea discharge is believed to be something produced by normal operation and not by any damage of the nuclear power facilities".

http://www3.nhk.or.jp/news/html/20110608/t10013401701000.html describes the water intended for discharge as being sea water from the tsunami wave which accumulated in places such as the turbine buildings and the reactor buildings and has since been moved into tanks (the move into tanks is mentioned only in the video, not in the text). It says that the Cesium (concentration ? yearly amount ?) is 30 times above the allowed standard (video only), and the Cobalt 60 concentration is 1.5 times above the allowed standard (text only) without providing any clue as to where this Cobalt is coming from. The video worries for the cesium only while the text worries for the cobalt only : this is a bit strange.

Keiji Miyazaki, a professor emeritus of reactor engineering at Osaka University, said the reported radioactivity levels and composition of isotopes in the water suggested any issue at the plant was relatively small.
(...)
The 3,000 tons of water—a bit more than would fit into an Olympic swimming pool—contains radioactive cobalt 58 and 60 isotopes, iodine 131 and manganese 54, Tepco said Wednesday. Their levels are below the legal limit for discharge water set in Japan, whose limits tend to be stricter than other international standards.

However, levels of cesium 134 and 137 isotopes in the water—at 2 and 3 becquerels per cubic centimeter, respectively—exceeded the legal limits of 0.06 and 0.09 becquerels.
(...)
Neither body [NISA or Tepco] addressed why the water remained onsite, however.(...) NISA said it was possible the water could have corroded some piping, causing leakage of radioactive materials.

JUNE 9, 2011 Second Japanese Plant to Dump Tainted Water by Mitsuru Obe : http://online.wsj.com/article/SB10001424052702304259304576373150813737000.html

A Yomiuri article mentioned at https://www.physicsforums.com/showthread.php?p=3345550#post3345550 took the view that the cesium flew from Daiichi to Daini.